Tunnel field-effect transistors (TFETs) are typically recognized as successors of metal-oxide semiconductor field-effect transistors (MOSFETs) because of their absence of short-channel effects and of their resulting low off-currents. Another advantage of TFETs is that the subthreshold swine can be less than 60 mV/dec, which is the physical limit of conventional MOSFETs, such that potentially lower supply voltages can be used. Different TFET integration approaches exist for both horizontal and vertical technologies.
At least part of the intrinsic channel region of the TFET device is situated between at least part of the highly doped source region and the gate structure. A disadvantage of this approach is the presence of an intrinsic channel between source and drain, so called p-i-n TFET. This region must be wide enough to act as a blocking layer for band-to-band tunneling current which is not controlled by the gate, otherwise defined as leakage current. This region (tunnel region) creates a high on-current resistance and increases the device dimensions. TFETs having all tunnel paths turn on at the same time for fast switching and low operating voltage are in urgent need. In addition, high band-to-band tunneling current in the on-state which means a small effective band gap is necessary at the tunnel junction.